Scilab Function
Last update : 12/1/2004

p_margin - phase margin

### Calling Sequence

  `[phm,fr]=p_margin(h)`
  `phm=p_margin(h)`

### Parameters

- `h`: SISO linear system (`syslin` list).
- `phm`: phase margin (in degree)
- `fr`: corresponding frequency (hz)

### Description

The phase margin is the values of the phase at points where the nyquist plot of `h` crosses the unit circle.

### Examples

    h=syslin('c',-1+%s,3+2*%s+%s^2)
    [p,fr]=p_margin(h)
    [p,fr]=p_margin(h+0.7)
    nyquist(h+0.7)
    t=(0:0.1:2*%pi)';plot2d(sin(t),cos(t),-3,'000')

### See Also

`chart`, `black`, `g_margin`, `nyquist`,

### Author

S. S.